Liquid fuel supply system for aircraft combustion turbines



1955 G. B. R. FEILDEN ETAL 2,700,415

LIQUID FUEL SUPPLY SYSTEM FOR AIRCRAFT COMBUSTION TURBINES Original Filed 001:. 16, 1945 3 Sheets-Sheet l Jan. 25, 1955 I G. B. R. FEILDEN ET AL 2,700,415

LIQUID FUEL SUPPLY SYSTEM FOR AIRCRAFT COMBUSTION TURBINES Original Filed Oct. 16, 1945 3 Sheets-Sheet 2 ll Fig.2. ||7

G. LIQUID FUEL SUPPLY SYSTEM FOR AIRCR Jan. 25, 1955 Original Filed Oct. 16, 1945 United States Patent LIQUID FUEL SUPPLY SYSTEM 'FORfA-IRCRAFT COMBUSTION TURBINES Geoffrey Bertram' Robert Feilden, Lincoln, Daniel Norman Walker, Dunsfold; andEilwin'Laurence Me'eson,

Golders Green, London, England, I assignors, to Power sets (Research & Development) Limited, London, Eng land, a British company Continuation ofapplicatiOnSerial- No; 622,494, October is, 1945: This application February 19,1951-,Serial No. 211,602. lln'GreatBritainc'tober '3tl; 1941 Section 1, Public-Law 690 -August 85'1946} Patent expires. October r3 0,-- 1961 This invention relates to fuel systemsfor engines, or

propulsive systems primarilyfor aircraft and :of thew-kind comprising a compressor in the air output ofwhich liquid fuel is burnt, the resultant energised gaseous mixturedriving a gas turbine practically the whole shaft power output of which is devoted 'to drivingthe:compressor whilst the residual energy of the exhaust. gasesz is that;

which is utilised. Such engines or propulsive systems have the feature that they maintain and adjust their fuel/air ratio automatically andconse'quently they arecontrollable by regulation of the rate of fuelsupply to the combustion system thereof. If in any 'given-stablexrunning. condidens the rate of fuel supplied is increased the-rotational speed increases (during which increase there is temporarily an increase in the fuel/ air ratio). The fuel/air-ratioabeingy interms of mass it follows that if there'were a fixed,

The primary object of the-invention is :to afford a fuel.

system which is adapted'to the requirements'of such en,-

gines or propulsive systems more especiallyiwlr'en; applied.

to aircraft, in which application some formrof'altitu'de control is likely to be necessary The iDVClitlQlidf ap; plied in'its entirety has a'large numberof:objectspittnot only seeks to provide'for what .mayl be called' ordinary= running control in an extremely simple manner but also for governing in regard to overspeedi'ng1or-at--selected speed or both, governing in respect of altitude,-the-preservation of a wide range of speed control-movement at all:- operational heights, starting'and stopping, andinrel'ation to other functional factors. The invention alsouseeks to:

provide fuel systems of considerable simplicityzwhich are usable by the operation (in running) of asingle control element; Thus, whilst'in an ordinary"aero-engine'1installation the pilot may haveto control -a throttle mixture devices and airscrew control;- and other details,aand may be required to exercise hisskill andjudgment in interpreting a certain numberof-instrumentsl-in orderproperly to use these controls; in thef-I installation contemplated by this invention be simply has-one control which he can regard either as a -control of"R. P-.' or of useful propulsive thrust and there 11103416661 except for the sake Qf infQrmatiOn; forshim to observe instruments closely. The invention further affords means for rendering as automatic and simple as :possible'tbepro cedure'of starting and stopping; It can:be-assumedthat engines or systems of the-kind'statedhave certaimfairly well defined idling speeds and that below-wthese speeds they are not satisfactorily self-driving. The actual idling; speed of such an engine maybe determinedby its ability to accelerate 'satisfactor-ilvwhen thefuel supply-is; in:

creased. The systems proposed by the invention enable a starting procedure to be adopted which is operationally extremely simple and in which. -certain safeguards are provided. The invention includes a system-or; methodof starting which consists in: usingthe elements andar-i rangement prescribed by the-mvention, irra certainway:

ICC

2 Functionally, however, the procedure for starting involves rotating the-turbine and-compressorzto a certaincomparatively low speed so astodnduce a-fiow of air through 'the' engine, supplying tfuel ina; proper condition to be ignited and thereafter to. burn, igniting the-fuel, and thereafter further speedingupthe R. P. M. until a speed is reached at which the engine :becomesj-self-driving, and controllable.

In'order to meet flyingconditionsuit is desirable to 611-1:

sure that a. certainminimum speedzis provided for, which can'beyregarded-as theidling speed and this, in general: terms is the same as, or-is"ofthe same order as, the

speed at which the engine .canvberegarded'as controllably self d-riving; we shallcall; it the idling speed. It" is. also obviously necessary to afford means for stoppingv lhC'Bl'l-i gine andit is operationally. preferable that starting'means should be such as to be useful during flight. tion seeks to fulfil these requirements and .to conform with the startingprocedure indicated, and'also to'take into account the other properties and limitations of such enginesandpropulsive systems; It will be assumed that the meansg by whichthe 'fuel' is delivered into the engine prior to combustion are such as to have a well definedpressure/flow characteristic operating over whatever range conformswith the performance of the engine. For: convenience such means will be called'burners; it is at present contemplated that the fuel will' be delivered into the combustionsystem' through burners involving variable orifices or other means whichr define their pressure/flow characteristics.

According to the invention in. its broadest aspect a fuel supply system for an engine or-propulsive installation of' the kind'stated, comprises a fuel pumpdriven by the engine and of a substantially positive-displacement type,-

a'relief' valve or equivalent means for controlling the pres-. sure of the delivered fuel, burners or equivalent means; for" passing fuel into the engine for combustion at rates.

related to the pressure of-fuel applied thereto, and control valve or throttle means between the fuel pump and the burners for varyingthe effective pressure of'supply to the burners. The throttle maybe a simple valve such as a screw valve operatedwbyyhand or it may be operable by speedor pressure sensitive means orit may have both characteristics; i. c; it maybe manually controllable andgoverned by speed or pressure; It may comprise two ormore valves each of which is controlled in a different way, for example 'there maybe a manuallycontrolled valve; in: series with-a. valve controlled by. means of a governor in accordance with the engine speed. The pump. is-preferably a gear type orlike pumppositivelydriven.

by the engine and it should have asufiicient capacity to deliver the-maximum engine requirement in any foreseen'conditionof running; its minimum capacity-will therefore presumably be selected having regard :to the rate of supplyrequired during the most rapid acceleration:

anticipated- The pump may. be supplemented by a second pump utilised in starting and in that case preferably driven by a'starter motor. In'another arrangement the operation of 'tlie'pump, at starting may be supplemented by the provision of a pressure accumulator in place of the second pump in a manner which will be enlarged upon later. The fuel pressure controlling means'may be a springrloade'd reliefrvalvle in a simple form or a relief valve the operative pressure of which is determinedby a .variable loading varied by hand, by speed or pressure responsive governor or, asisprefe'rred, by means sensi-.

tiveto= the atmospheric pressure in. which the engine is operating In this last; casethe relief valve is preferably spring-loaded and the force exerted by thev spring is varied (through servo-means) in accordance with'the pressure atwhich the engine draws in air.

Preferably it is' arranged'that the pressure control by the relief valve is made interdependent with the local atmospheric 'pressure, or the local atmospheric pressure plus'qany Pitot pressure to' which the air intake-of the engine is exposed or to some'pressure between these two; present investigation contributes the feature, that the controllingpressure should be'approximately the atmospheric pressurepltis 0.6 of the Pitot pressure, and'the pressure sensitive elementmavberendered susceptible to such proportion for. example, by; connecting it to a. tapping at a suitablep'osition i113. Ventur i tube.or,.sotne..,other passage,

Patented Jan. 25, v 1955 The inven-.

in which there is a velocity and consequently a pressure gradient. The atmospheric pressure or this pressure plus all or some of the Pitot pressure, is for convenience called the ambient pressure. By such means the relief valve can operate as a speed governing device for the engine.

In addition to the elements above set out there is preferably provided a stopcock, closing of which prevents any fuel from reaching the engine; and there may be nonreturn or check valves suitably located in the system to determine minimum pressures at which fuel will flow, and also to keep pipelines full. In conjunction with the throttle means stated there is preferably means to enable fuel to by-pass such throttle means for idling, the by-pass flow itself being controlled in accordance with the fuel pressure on the burners or manually or in accordance with some other factor such as speed.

In order that the invention may be better understood the following describes a practical embodiment of it, together with mention of various possible alternatives or elaborations.

The drawings herewith show, in

Fig. 1, a diagram of a fuel system according to the invention.

Fig. 1A shows an alternative of one part of this.

Fig. 2, a sectional view of the barometrically-controlled relief valve.

Fig. 3, a sectional view of the proposed stop-cock.

Fig. 4, a sectional view illustrating the speed governor.

Fig. 5, a sectional view illustrating the combined throttle and by-pass (idling) valve.

The main fuel pump 1 is driven by the engine, and is preferably a simple gear-type pump. It is supplied from a fuel tank 2 through a pipe 2A with low-pressure stop-cock 2B and low-pressure filter 2C. The pump 1 delivers fuel by the main pressure pipe 3, through a high-pressure filter 3A, through manual throttle means indicated at 4, governor 5, high-pressure stop-cock 6, dump valve 7, to a manifold ring 8 from which branch the fuel burners 9. From the pipe 3 is a branch 33 leading to a relief valve indicated at 10, the relieved flow or spill from which returns to the tank 2, along the pipe 11 which may also return other spillage or leaks to the tank, such as that coming from the throttle unit 4, by the connection 11A. In parallel with the pump 1 is a supplementary pump circuit, comprising a feed branch 12A, pressure branch 12B, and pump 12 driven by the engines starter-motor indicated at 12C. In the branch 12B is a non-return valve indicated at 12D. A burner pressure gauge 14 is connected by a branch 14A to the pipe 3 at a location where it will respond virtually to the pressure at the burners when the system is operating, whilst indicating the pressure developed in the system when for example, the cock 6 is closed. The dotted-in pipes represent drains from various glands, etc. which may leak a little.

In Fig. 1A, the modification is illustrated, wherein between the governor and cock 6 a pressure accumulator 15 is provided on the pipe 3, and a non-return valve 15A immediately upstream in pipe 3, prevents its contents discharging back through the system when the engine is stopped.

The system of Fig. 1 thus outlined operates as follows. It is presupposed that the burners 9 deliver fuel for combustion into the engine, at a rate proportional to the fuel pressure applied to them. It is found preferable to use burners which have as nearly as possible a linear pressure/flow characteristic, though this is not believed essential.

To start the engine the cocks 2B and 6 are opened and the starter-motor 120 is energised. The engine is thus accelerated from rest, and the pump 12 as well as pump 1 are driven. It is not economical to make pump 1 sufficiently large in capacity, or to arrange its gear ratio with the engine, in such a Way that its output in pressure and rate is adequate for starting, hence the provision of pump 12. At starting therefore it can be assumed that pump 12 is the mainly-operative source of fuel. It draws fuel by 2A, 12A, and delivers it into pipe 3 via 12B; so long as the motor 12C is running. This fuel, at an insufficient pressure to open the relief valve 10, flows by pipe 3, throttle by-pass (to be described) in 4, to the valve 7 (to be mentioned) and thence to the burners 9. Simultaneously, suitable igniting means in the engine start the required combustion. The engine being further accelerated partly by the motor 12C and increasingly by its own power, the pump 1 begins to be operative and quickly raises the fuel pressure in pipe 3. When this pressure exceeds that due to pump 12, the non-return valve 12D closes, and matters are so timed that in this phase of operation the motor 12C is cut out so that pump 12 stops, and the engine is now selfdriving on the pump 1, its speed however being limited by the by-pass in the throttle unit 4.

To stop the engine all that is required is to shut oh the cock 6. When this is done, the valve 7 connects the burner-manifold 8 to atmosphere so that it drains, and moreover any air pressure in the engine, to which the burners are exposed, tends to blow. back through the burners and out of valve 7, preventing dribbling of the burners and emptying the manifold 8 which is found to be good practice.

The valve 7, which is called a dump-valve because it dumps unwanted fuel accumulation to waste, is a change-over valve operated by pressure in the pipe 3, and it is more fully described in co-pending application No. 597,911, filed June 6, 1945, and now Patent No. 2,619,162, by Geoffrey Bertram Robert Fielden. When there is operative pressure in pipe 3 downstream of cock 6, this valve connects pipe 3 to manifold 3, but when this pressure ceases, the valve opens manifold 8 to an atmospheric drain.

Reverting now to the condition when the engine is running at idling speed, if the throttle at 4 be opened the burner pressure is increased beyond that corresponding to idling, and consequently the rate of fuel supply is increased and the engine accelerates, until a new speed is reached when the mixture strength of the engine is again stabilised (corresponding to the new throttle setting). Since the pump 1 is selected and geared to deliver fuel at a higher rate than the corresponding engine demand, a proportion of the fuel pumped passes by 313, to and through the relief valve at 10, and returns to the tank 2 by pipe 11. As will be described, the relief valve loading is varied with ambient pressure, so that the lower fuel demand which arises with lowered ambient pressure, is catered for by a drop in pressure in pipe 3 and correspondingly less flow through the burners 9. This enables the action of the throttle to be simplified; if there were no such provision, then as the ambient pressure varied the pilot or user would have to re-adjust his throttle to maintain a selected engine speed, and this re-adjustment would be theoretically continual during any change of height. Moreover, the range of movement of the throttle control would vary according to height, and the total range for throttle control if reasonably adequate near the ground, would be impractically small at altitude.

The governor at 5 is, in effect, a second throttle valve in series with the manual throttle, but only operative by closing at a selected top speed, by the action of centrifugally operating weights driven by the engine.

The device of Fig. 1A can be employed as a substitute for the pump 12. Where it is used, the starting procedure is as follows. The cock 2B is opened, and the motor 12C energised. The output of pump 1 then charges the accumulator 15. Thereafter the cock 6 is opened, and the contents of the accumulator 15, under its pressure, pass to the burners 9, the initial burst of pressure being adequate to ensure atomising of fuel and starting conditions generally. Meanwhile the pump 1 is of course still delivering, and the engine will accelerate to idling speed as required. Upon stopping by closing the cock 6, the pressure in the accumulator which can be assumed to be above the maximum required for starting, will remain stored because of the closing of the non-return valve 15A, and subject to drop by leakage is available for the next start. The spring or elastic medium in the accumulator may be selected to afford an appropriate rate.

The general operation of the system having been described, we shall now show how the more important components are made and operate.

Fig. 2 shows the barometric relief valve at 10. This is a servo-operated device, using pressure-fluid as its servo medium, which can either be engine lubricating oil, or the fuel itself. It is assumed that the servo-fluid is supplied at substantially constant pressure, this being achieved by appropriate valve means of any suitable known kind.

The relief valve unit comprises a casing or body 101 having a relief-valve seat 1012 and relief valve 103 which is on a stern and spring-urged towards the seat by a pack of springs 104 selected to give the required rate. The spring pack 104 is housed in a cylindrical chamber, and reacts on the underside of a piston 105 sliding in this chamber. To

5 the underside' o'f' the'valve 103 is 'supp'lied tlie' fuel -frorn the p1pe '3B (Fig. l) at the--=full pressure ot the pump 1;. Fuel raising and passing'atheiva'lve 103 'is collectedfin'ithe" spring chamber and escapes through a: union 106, to re-' turn by pipe 11 to=thetank 2; The-loadof the springpac-k 104'onthe valve 103 is determined bythepositionofthe piston-105." Servo-'fluidpressu're"acts aboveithispistonin the space 107, Whichicommunicate'sby a du'cti 108 with a slide valve port controlled iby aiislide valve1109rwhich either admits servo fluid (Whi'Ch iS supplied through'union 110) to the space 107,- or emits2 itfr'omTthe space-(through union 111). The valve tl09 isrpreferably so dimensioned in relation to its port 'thatiwhemthe valve is balanc'edit allows a very small: .flow fro'rn'rlltl toill, maintaining the servo pressure in space 107:.

The valve 109"'is':'moved'.through arsternv109A', bythe deformations.ofaflexible sylphombox'lll which is evacuated and acts as'a barometric device-r The'ambient' pressure communicates withitheninteriorofa chamber 113 through a'Ivent"114 whichzis::suitablyi'protected to prevent ingress of foreign matter; The-Syl'phon box 112, housed in the-chamber 113,'isimo1.mted atits lower end on a guided rod 115rwhichiby means of'a forked end is engaged by a rocker 116= borne at 116A',*thetail of which rocker is acted upon 'byna pushrod -117 'slidable instructure of .the body 101', the upperend" of the pushrod abutting against. the underside of .thepiston 105; This push and rocker mechanism'z'acts -as a-"follow-updevice, because the position-zof the piston 105-determines the-location of the-box 112 within.itschamber'113; thus when an expansion of'the'boxl112 causes'valve 109-to rise,emitting servo-fluid from:the space-107,- the piston 105 rises (by influence of :the 'spr ing;;packi 104 thereby reducing the fuel pressure required to opennthe valve-103', and simultaneously the :pushrod 117 "rises; dropping the :bot-' tom of the box 112.: This::train -of action corresponds with a fall inam'bientpressure in 113,-i c. with an increase-of .altitude- (or= decrease-:offorwardspeed in a case where Pito't pressure iswa-rfactor); Its'result in the fuel systemis to reduce -thesupply-pressure for a given set of conditions-thus to-:reduce-the fuel supply-to the engine.

The foregoing. description,- asvwell as other descriptions herein -of separater components," are intended for guidance as to functiontrather than for-manufacture; where theconstruction lis not-obvious' from the drawings, it will nevertheless be" sufiicientirfor one skilled in the art Who has acquainted-himselfwwiththe function,-to put the device intopracticer It will be observed that the barometricallyj controlled relief valve of-.Fig. 2 embodies jacketting as at 1185-this'iis intende'dfor circulation of 'the fuel in order to maintain-reasonable and uniform tern-- peratures' in :the assembly Theiunion-at 119 'is'for' drain of leakage ormoistures Fig. 3 representstthe: stop-eock-6:in-Fig. 1. The=body structure 30-1-has an inlet=union.-302 and outlet-303'. An operating spindle 304 passesinto'the body andhas'a flange at 304A, between whichflange and a seatrin the body 301 is a synthetic-rubber washer -305A-,.fr sealingpurposes. The spindle 304-alsoahas anieccentriopin 305 formed on itsinner end; and this-engages a transverseslot-in a valve stern 306 .which .is= guided in suitable-bores inthe body 301. The stem carries a -valve-head=307 co-operating with a seat in the body,- and preferably urgedtowards-this seatbya spring 308.- When:the-spindle 304 is appropriately partially rotated, thez-valve is -opened and contrarotation closes it.- It is-foundthat such a cock is well suited to therelativelyihigh pressures of fuel used'and requires only a comparatively :low-torqueafor its operation.- It is dcscribed-becauseno ordinary types of commercial cock'over. a fairly wi'derange'teste'd, has been foundto give as satisfactory a result.

Fig. 4 shows diagrammatically thetype of governor used at 5 in-Fig.- 1,. considerably simplified for ease of functional description. A system of'flywei'ghts 401 is whirled by an engine-drivenspindle-402and under centrifugal influence urges a collar. 403 axially against a spring 404, which-inpractice. is adjustable or selected for a chosenspeed of operation. The collar 403 on a rod 403A, causes thisrod to move axially under. governor operation, thus rocking alrocker 405 whichv in turn actuates (by a stem406) a slide. valve 407 which is a pressure-'balanced'valve controlling the effective opening of a series of: fuel portsl408 whichinter-connect an inlet union. 409 and-outlet 410. The ports 408 are stepped axiallyyand(overlaprslightlyj in:. this!-.sense, and the endia portiss so placed thati withrthea valve-407 ineits position of maximumclosure theiend port isalways clear-,1 sothatw the governorwcannot completely shutoff-the fuel flow in 5* the pipe? in:which .it isvconnectedv In' practicetheglaud- 406A'of the stem-406 is replaced by -a series of elastioor; pliable diaphragms; t0-'avoid frictionalelfects which militat'e against accurate governing; A drain ="l1n10n' iS- -pro= videdat 411.- 10 It will beappreciated thatsuchia-governor is in effect; a second-throttle valve inseriesvwiththe-manuahthrottle at 4 in Fig. 1. i

Fig. 5 illustrates the throttle valve and bypass unit; 4 in Fig; 1. Ther functionof-this unit inthe'system is of 1nconsiderable importance-in'thatc-it enables a conventionalsimple single-lever- -throttle control. tobe used; whilst pre-p cludinginadvertent: shuttingpfi :of fuel supply :to thegen gine. Itisto ber-understood thatrthis is more important} in the type of -eng-ine..under consideration than..in,..sa y,. Qtjfkan orthodox --reeip rocating.zinternal combustion enging.

for in the present case ifv fuel supply v ceases there is. no. continuously :operating,ignitionsystem to re-ignite it. when: the supply is restored- The device. comprises a body-501 .supportingin a bore, zdfa 'tubularseat elementt502. for a so-calledmeedle-type. van/e503. The seatingof the. valve is. adjuStabIeIeIa-J- tively to a .given. .closeds'position of the. valve- 503, by. screwing. Thusadjustment need not involve the throttle operating mechanism. The valve 503. is. carried by a,

aot screwed spindle 504 operable. by, external means and-Q glanded. through the bodyj501. Holes in. the. element 502-allowfuel to ent'er'it from. a. duct 505 connected to the fuel pipe 3; The. downstreamside of the valve 503 l is a duct 506 leading passed. fuel to an outlet union 5.07 J-and so. to. continuation ofthe pipe 3. The valve 503- is however by-passed by.a .duct'505A'which leads to a ring" of ports 508 in a. cylinder 509' 'm0unted in the body 501.. In thiscylinder slides a by-pass controlling valve 510,-v which is a tubulartsleeve with a header floor'at 510A: 40 against. which bears: a spti'n'gjll centred on ar coaxial. stern 512A of asettingpiniSlZ which is rotatable within? an adaptor 516 screwed into the body .501. The adapt or 516 retains the cylinder 509 in position, awasher 516A being interposed.between the inner end of theadaptor and the adjacentend of the'cylinder.- The washer has an-external peripheral. groove 516B and transverse holes 516C for draining fluid'from the chamber containing the. spring- 511 through union 515; The stem 5122A is fluted and on it is unrotatablyslidable a-collar 513 which isexternallythr-eaded' and which screws along a threadin'the; adaptor 516-when-the-pin 512 is rotated. The:pin'51Z has a flanged head 512C engaged by a locking nut 512D threaded onto the outside of the adaptor 516. A washer 1 5123 is used .to effect a seal betweenthe head 512C and the adaptor- 516. It is lseenthatthe spring 511 reactsagainst the collar 513 and its' initial set load is adjustable', by rotation of .the stem 512A which is thereafter locked by 512D. i p

The valve 510 is externally flanged at 510Bfandhas' ports 510C toregister (when the valve is idle) withthe ports 508. By these registering ports, fuel from 505A passes into the valve the end of which is open toduct 506.. The flange 510B seats through a washer, 5101), against a step -in the bore ofgthe: cylinder 50?, when thevalve is fully. open; in its other position of rest however, with spring 511'c0mpressed, the valve seats against a washer 514, preventingleakage. Between the two ex tremes a certain amountof'leakage is to beexpected and this is drained from the union 515; I When the valve 503. is closed and theengine starting procedure is commenced, .fuel passes through 505; 505A; 508,-.510C, into 506 and so to the burners. As acceleration continues and fuel pressure increases at the burners, i. e. in 506, the valve is pushed back against itsspring- 511, progressively cutting off the opening of ports 508," limiting the burner pressure to a predetermined value (determined-by the elfective force of the spring) and thereafter maintaining this value. The bypass valve short, acts as a pressure-reducing valve; When the throttle valve 503 is'openedthe' pressure in 506 rises, con: sequent upon the increaseinengine speed and higher pressure developed by. the engine driven pump, 1. This" increased pressure causes the complete 'closure of the valve 510 which then bottoms on the washer 514." When the throttle valve503is closed," the pressure- 506 falls (due to reduction in engine speed) until the valve 510 opens again to maintain the constant pressure corresponding to the required idling condition.

The fuel system above described has been operated satisfactorily with kerosene fuel oil, and like fuels, at idling pressure and maximum pressures of the respective orders of 30 lbs. sq. in. and 500 lbs. sq. in., with rates of flow in the burners varying substantially linearly with pressure. There appears to be no reason why it should not operate with widely different pressures, but the devices as shown are intended primarily for employment in approximately this range.

We claim:

1. In a turbomachine including a turbine, means for continuously supplying a compressed working fluid thereto, liquid fuel combustion apparatus for heat energizing said Working fluid prior to its entry into the turbine, at least one liquid fuel injection nozzle constituting a part of the combustion apparatus, and a systern for supplying fuel to the combustion apparatus, wherein said fuel supply system comprises a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above the idling speed of the turbine fuel is supplied by the pump at pressures of the order of hundreds of pounds per square inch and the fuel capacity of the pump exceeds the demand of the combustion apparatus, a pressure pipe connecting said pump to said nozzle, means responsive to the output pressure of said pump to maintain constant the pressure of fuel passed toward said nozzle and a throttle valve in said pressure pipe between said pressure responsive means and nozzle, said throttle valve having a throttling orifice distinct from the orifice of the nozzle, means to adiust the throttle valve to vary the rate of admission of fuel to said nozzle over a range from a maximum corresponding to full speed requirements to a minimum corresponding to idling speed requirements, and hence to vary the fuel pressure at said nozzle over a range of the order of hundreds of pounds per square inch, means independent of said pump for delivering fuel toward said nozzle during starting and means responsive to a predetermined fuel pressure in said pressure pipe for rendering said independent means inoperative.

2. In an aircraft propulsion turbomachine including a turbine, means for continuously supplying a compressed working fluid thereto and liquid fuel combustion apparatus for heat-energising said working fluid, the improvement that comprises a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied by the pump at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above the idling speed of the turbine the fuel supply capacity of the pump exceeds the demand of the combustion apparatus, a plurality of fuel injection nozzles constituting a part of the combustion apparatus, a pressure pipe connecting said pump to said nozzles, means res onsive to the output pressure of said pump and to ambient pressure to maintain a predetermined order of difference between ambient pressure and the pressure of the fuel delivered toward said nozzles with the pressure of the fuel exceeding ambient pressure, and a throttle valve in said pressure pipe between said pressure responsive means and said nozzles for controlling in common the rate of admission of fuel to all of said nozzles.

3. In a turbomachine including a turbine, means for continuously supplying a compressed working fluid thereto and liquid fuel combustion apparatus for heatenergising said working fluid prior to its entry into the turbine, the improvement that comprises a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above the idling speed of the turbine the fuel supplied by the pump exceeds the demand of the combustion apparatus, a plurality of fuel injection nozzles constituting a part of the combustion apparatus, said nozzles being designed for operation at hundreds of pounds per square inch of pressure, a pressure pipe conmeeting said pump to said nozzles, means responsive to the output pressure of said pump to maintain constant the pressure of fuel passed toward said nozzles, and a valve system in said pressure pipe between said pressure responsive means and said nozzles for controlling the admission of fuel to said nozzles, said system including a passageway having a throttle valve therein, a low pressure connection by-passing said throttle valve passageway, a normally open valve in said connection and means for closing said normally open valve.

4. In a turbomachine including a turbine, means for continuously supplying a compressed working fluid thereto and liquid fuel combustion apparatus for heat-energizing said working fluid prior to its entry into the turbine, the improvement that comprises a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above the idling speed of the turbine the fuel supplied by the pump exceeds the demand of the combustion apparatus, a plurality of fuel injection nozzles constituting a part of the combustion apparatus, said nozzles being designed for operation at hundreds of pounds per square inch of pressure, a pressure pipe connecting said pump to said nozzles, means responsive to the output pressure of said pump to maintain constant the pressure of fuel passed toward said nozzles, and a valve system in said pressure pipe between said pressure responsive means and said nozzles for controlling the admission of fuel to said nozzles, said system including a passageway having a throttle valve therein, a low pressure connection by-passing said throttle valve passageway, a normally open valve in said connection and means responsive to the attainment of a predetermined pressure in said passageway for closing said normally open valve.

5. In a turbomachine including a turbine, means for continuously supplying a compressed working fluid thereto and liquid fuel combustion apparatus for heat-energising said Workingfluid prior to its entry into the turbine, the improvement that comprises a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above the idling speed of the turbine, the fuel supplied by pump exceeds the demand of the combustion apparatus, a plurality of fuel injection nozzles constituting a part of the combustion apparatus, said nozzles being designed for operation at hundreds of pounds of pressure, a pressure pipe connecting said pump to said nozzles, means responsive to the output pressure of said pump to maintain constant the pressure of fuel passed toward said nozzle, and a valve assembly in said pressure pipe between said pressure responsive means and said nozzles for controlling the admission of fuel to said nozzles, said assembly including two intercommunicating passageways, a throttle valve in one of said passageways, a piston valve in the other of said passageways exposed to the pressure of the passageway containing said throttle valve at a position downstream of said throttle valve, and means resiliently biasing the piston valve to open position, said piston valve moving to closing position upon the attainment of a pressure in the throttle valve passageway sufficient to overcome the bias of said resilient means.

6. In a turbomachine including a turbine, a compressor driven by said turbine, and a liquid fuel combustion apparatus continuously receiving compressed air from said compressor and connected to supply combustion products to said turbine, the provision of a system for the supply of liquid fuel to said apparatus comprising a plurality of liquid fuel atomizing nozzle burners constituting a part of said combustion apparatus, a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above idling speed of the turbine the fuel supply capacity of the pump exceeds the demand of the combustion apparatus, a pressure pipe system connecting said pump and said burners, throttling means in said pipe system between said burners and said pump, said throttling means being adjustable to vary the rate of fuel flow from a maximum corresponding to full speed to a minimum corresponding to idling speed, means responsive to the output pressure of said pump to maintain constant the pressure of the fuel reaching said throttling means, shut off valve means in said pressure pipe system to isolate said burners from said throttling means, and pressure responsive valve means in said pressure pipe system between said throttling means and said burners to prevent delivery of fuel below a pressure at which said burners can effectively atomize.

7. In a turbomachine including a turbine, a compressor driven by said turbine, and a liquid fuel combustion apparatus continuously receiving compressed air from said compressor and connected to supply combustion products to said turbine, the provision of a system for the supply of liquid fuel to said apparatus comprising a plurality of liquid fuel atomizing nozzle burners constituting a part of said combustion apparatus, a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied at a rate functionally related to turbine speed, the effective speed of the driving connection and the output capacity of said pump being so correlated that at all speeds above idling speed of the turbine the fuel supply capacity of the pump exceeds the demand of the combustion apparatus, a pressure pipe system connecting said pump and said burners, throttling means in said pipe system between said burners and said pump, said throttling means being adjustable to vary the rate of fuel flow from a maximum corresponding to full speed to a minimum corresponding to idling speed, means responsive to the output pressure of said pump and to ambient pressure to maintain a predetermined order of difference between ambient pressure and the pressure of the fuel delivered towards said throttling means with the pressure of the fuel exceeding ambient pressure, and shut off valve means in said pressure pipe system to isolate said burners from said throttling means.

8. In an aircraft propulsion turbomachine including a turbine, means for continuously supplying a compressed working fluid thereto, and liquid fuel combustion apparatus for heat-energising said working fluid, the improvement which comprises a positive displacement type fuel pump, means establishing a driving connection between said pump and the turbine so that fuel is supplied by the pump at a rate functionally related to turbine speed, fuel injection nozzles constituting a part of the combustion apparatus, a pressure pipe connecting said pump to said nozzles, a throttle valve for controlling in common the rate of admission of fuel to all of said nozzles, and means responsive to the output pressure of said pump and to ambient pressure to maintain a predetermined order of difference between ambient pressure and the pressure of the fuel delivered to said throttle valve.

9. In an aircraft propulsion turbomachine including a turbine, means for continuously supplying a compressed working fiuid thereto, liquid fuel combustion apparatus for heat-energizing said working fluid, a plurality of fuel-injection nozzles constituting a part of the combustion apparatus, a positive displacement type fuel pump driven by said turbine, so that fuel is supplied by the pump at a rate functionally related to turbine speed, a pipe connecting said pump to said nozzles for delivering fuel under pressure to said nozzles, and fuel supply con trol means connected to said pipe, the improvement that said control means includes means responsive to the fuel delivery pressure and to ambient atmospheric pressure, to maintain a predetermined order of difference of ambient pressure from the pressure of the fuel delivered, and a throttle valve connected in the path of said delivered fuel, for controlling the rate of admission of fuel to all of said nozzles in common.

References Cited in the file of this patent UNITED STATES PATENTS 1,857,556 Lasley May 10, 1932 2,078,957 Lysholm May 4, 1937 2,219,994 Jung Oct. 29, 1940 2,280,835 Lysholm Apr. 28, 1942 

